Method of and apparatus for dressing grinding wheels



June 1959 H. METZGER ETAL 2,889,822

METHOD OF AND APPARATUS FOR DRESSING GRINDING WHEELS Filed June 10, 1957 4 Sheets-Sheet 1 INVENTORS:

HAROL ILLER ATT'Y LEOPOLD H. METZBE-Q L. H. METZGER ET AL June 9, 1959 METHOD OF AND'APPARATUS FOR DRESSING GRINDING WHEELS Filed June 10, 1957 4 Sheets-Sheet 2 INVENTORS:

FIG. 6

June 1959 L. H. METZGER ET AL 2,889,822

METHOD OF AND APPARATUS FOR DRESSING GRINDING WHEELS Filed June 10, 1957 V 4 Sheets-Sheet 3 INVENTORSI LEOPOLD H. METZEER ATT'Y BY HAROLD/@ILLER June 1959 L. H. METZGER ET AL 2,889,822

METHOD OF AND APPARATUS FOR DRESSING GRINDING WHEELS Filed June 10, 1957 4 Sheets-Sheet 4 FIG H INVENTORS: LEOPOLD H. METZ R HAROLD c. MILL BY M@MZ ATT'Y.

United States Patent METHOD OF AND APPARATUS FOR DRESSING GRINDING WHEELS Leopold. H. vMetzger, Glencoe, and. Harold C. Miller, Chicago, Ill., .assignors to Super-Cut, Inc., Chicago, 111., a corporation of Illinois Applicationlune 10,1957, Serial No. 664,570.

12 Claims. (CL 125-11) The present invention relates to a method of and an apparatus for truing abrasive grinding wheels .or the like and'it has particular reference to a novel tool and ,tool holder assembly of the kindv wherein the tool consists of a shank having mounted therein a diamond dressing stone adapted to be presented to a rotating grinding wheel for dressing purposes, the dressing actiontaking place. in either direction of traverse across the wheel surface, as well as having reference .to a novel method of using such tool and holder assembly during actual dressing operations. Still more specifically, the invention is concerned with adiamond-carrying mount or tool of novel construction wherein the diamond is crystallographically oriented relative to the .tool shank. axis and the tool holder is so designed that it will permit application of the diamonddressing stone to the rotating surface .of the grinding wheel at selected regions on the surface of the diamond and inselected vectorial directions relative to the crystallographic structure of the diamond on the one hand, and in a selected direction relative to .the rotating surface undergoing truing on the other hand, the selected regions on the surface of the diamond and the vectorial directions being such as to produce a greater overallresistance to abrasion on the part of the dressing stone than has heretoforebeen possible utilizing conventional diamond mounts and methods .of applicationthereof to the periphery of the grinding wheel, while-theseleeted direction relative to the surface of the grinding wheel beingsuch-thatmaximum dressing effect on the-surface undergoing treatment consistentzwith stone preservation such as minimum surface Wear,,freedom from fracture, chipping and otherforms ,of rupture will be attained.

It has long beenrecognized that a diamond dressing stone offers varying resistance to abrasion, depending-upon the. particular relationship betweeenthedirection of. abrasion across the contacting face of the stone and the crystallographic axes of the stone. For example, utilizing the system of crystallographic notation knownas Millers indices as described in a publication entitled Mineralogy, by Kraus, Hunt and Ramsdell, published. by McGraw- Hill Book Company of New York, fourth edition (1951), pages 15 and 16, adiamond is possessed of threebasic families of planes existing throughout thecrystal structure. These are the cube or (100) planes, the octahedron or (111) planes and the dodecahedron or (110) planes. These planes or families of planes willbe'referred to as such throughout this specification except when they occur on the surface of the diamond,underconsideration, at which time they will be termed faces, the indices being applicable to both internalplanes and external faces. Furthermore, the term plane will be used herein as being the broader term, it being inclusive of both internal planes and external faces. It is pointed out that such planes and faces possess, among themselves, hardness variations which render them resistantto abrasion in different degrees, and these planes also possess, within themselves, hardness variations of, a directional nature as will bedescribed in greater detail'presently, these phenomena cube edge.

being taken advantage of in practicing the present invention.

Infur-ther explanation of the system of crystallographic notation known as Millers indices, it is pointed out that a. crystal is based on a three-dimensional framework through 'which it is always possible to pass a-large number of parallel equidistant planes. The external crystal form of any substance is dependent upon the arrangement of its atoms, and due to. the great number of different chemical substances, an almost infinite variety of crystal forms is possible. To. assist in defining various. crystal forms, straight lines or axes are assumed to pass through the ideal center of each crystal. Crystal faces are not accidental surface phenomena but, are dependent upon the internal atomic arrangement, and inorder to determine the. position ,of a face on a crystal, it is referred to the crystallographic. axes. In the cubic system associated with adiamond, these axes intersect at right angles and form an axial cross. The axis extending. from front to rear maybe termed the a axis; the one from right to left the b axis; and the vertical axis the c axis. The distances atwhichany given plane intersects these axes are known as parameters and .the ratios .of these distances are known parametral ratios. In the Miller system of notation, the letters referring to the various crystallographic axesare not indicated, thevalues given referring to the a, b .and-c axes, respectively, in the order named. The reciprocalsof the parameters are. reduced to the lowest possible common denominator and the numerators then constitute the Miller'symbols known as indices. For example, the reciprocals of the parameters 2a:b:3c would be 1/2, 1 1, 13. Reducing to the lowest common denom nator, these, are 3/6, 6/6, 2/6. Hence, 362 constitutesthe corresponding Miller indices and are read three, six, two or expressed (362).

In the cube plane, a diamond offers a relatively lower resistance to abrasion when it is being abraded in a directionparallel to a crystallographic. axis, i.e., parallel to a It oifers appreciably greater resistance. to abrasion when it is being abraded from point to point on the plane, i.e in either; diagonal direction across the cube face. Within the cube plane, the magnitude of abrasive resistance varies vectorially between these two directions, the increments of abrasive resistance increasing as the direction of abrasion changes from parallelism with a crystallographic axis to a 45 angle with respect theretoin the plane.

Within the octadehedron plane, the resistance to abrasion offered by a diamond is greater in any direction than .theresistance which is offered in the cube plane or dodecahedron plane. An octahedron face exhibits itself on the surface of the diamond as an equilateral triangle and such faces. andplanes offer directional rwistance to abrasion in that when abrasiontakes place in the plane in a directionextending from a base to a point, the resistance to suchabrasion is greater than when the abrasion in the plane extends from the point to the base.

Within the dodecahedron plane, there are Wide vectorial. variations in resistanceto abrasion. As will be morelreadily perceived when exhibited as a rhombic face, the dodecahedron plane cuts two of the crystallographic axes but extends parallel to the third axis. Extending across two opposed corners of the rhombus in a direction at right angles to the unintersected crystallographic axis which will hereinafter be referred to as. the direction, the resistance to abrasion is relatively high. Atv right angles to this direction, the resistance-to abrasionis.considerably lower. In this (110) direction, within the dodecahedron plane, the resistance toabrasion isslightly, less than it is in the (111) or octahedron plane. As will appear presently when the nature of the invention is better understood, the relatively high resistance to abrasion offered by the dodecahedron plane as described above, particularly in the (110) direction in this family of planes, is utilized in a novel manner to produce a highly effective dressing of the grinding wheel with a minimum amount of wear on the diamond dressing stone, thus resulting in a comparatively long stone life and offering numerous other advantages subsequently to be set forth.

Heretofore, almost invariably, in conventional dressing procedure, utilizing conventional tools, it has been the practice to select a prominent point in the crystal structure lying on the cube plane and to present this point to the surface of the grinding wheel undergoing truing and effect the usual traversing operations until such time as a critical fiat has been worn on the surface of the diamond, after which the tool is rotated about its longitudinal axis so that a fresh abrading surface is applied to the grinding wheel. This procedure is repeated with the tool being periodically rotated, usually throughout an an gle of 45, as wear takes place until the diamond is worn beyond further usefulness. This method is followed for both peripheral, corner, and end face truing operations, as well as for any combinations thereof. Usually, the cube plane of the diamond stone is tipped through a slight angle, a 15 inclination ordinarily being employed, so that it will give a trailing cut to the rotating peripheral surface of the Wheel and, when this expedient is resorted to, the abrasive resistance of the stone is improved since successive adjustments of the tool results in alternate approaches toward the presentation of a previously mentioned hard octahedron face and the presentation of a dodecahedron face to the surface of the grinding wheel with the latter face being presented to the wheel in the hard direction of the plane, so to speak, which is to say that a point on the surface of the wheel moves into contact with the stone generally in the (110) direction. Utilizing this general procedure, it is obvious that the selection of suitable stones for abrasive purposes is limited to the more expensive grades of stones since not only is it necessary to select a well formed stone having a prominent point, but it is also necessary to select a stone of relatively large size to allow for the appreciable wear which takes place between successive adjustments.

The procedure outlined above is possessed of a still further limitation in that as successive flats are worn on the surface of the stone, the area presented by these flats becomes increasingly large until a condition is reached wherein it is necessary to reset the diamond and perform truing operations as outlined above which are predicated upon the selection of another prominent point in the crystal structure. This procedure is repeated as long as such prominent points are available and even under the most favorable circumstances, when all available points have been used, only about 20% of the diamond structure is left and the remaining 80% thereof is invariably in the form of a round generally spherical mass which is worthless for truing purposes and must be discarded.

The present invention is designed to overcome the above-noted limitations that are attendant upon the construction and use of such conventional grinding wheel truing apparatus and, toward this end, it contemplates the provision of a continuous repetitions method and of an apparatus by means of which the method may conveniently be carried out, whereby the diamond truing stone is at all times oriented relative to the grinding wheel in such a manner that its (110) direction is parallel to the direction of abrasion. According to the present method, the dressing edge, which extends in the (110) direction, may be the result of the presentation of the line or edge existing between two intersecting octahedron faces to the grinding wheel in the plane of rotation thereof, in which case wear will take place solely in the dodecahedron plane in a direction where resistance to abrasion is relatively great. In such an instance, the edge will be presented to the rotating surface of the grinding wheel head-on so to speak, wherein the bisecting plane of the two intersecting octahedron faces extends normal to the surface of the grinding wheel at the line of contact therewith parallel to the direction of abrasion. This truing position is maintained during an initial dressing phase for a period of time during which wear takes place and new dressing edges are constantly generated on the opposite sides of a fiat which is developed at the region of contact between the stone and the grinding wheel. These edges exist at the intersection of the lateral faces of the diamond and the newly generated fiat. Dressing operations are thus continued until such time as a critical fiat is obtained wherein it is no longer practical to continue dressing operations with the stone so oriented and, at this time, dressing operations are momentarily terminated and a new position is given the diamond by a lateral angular displacement thereof wherein one of the generated edges at one side or the other of the critical flat is presented to the grinding wheel surface in a position similar to the initial dressing position of the original dressing edge. In other words, this newly selected edge, which also extends parallel to the (119) direction of the dodecahedron plane, is presented to the rotating surface and dressing operations are resumed, thus commencing a second dressing phase of the method so that a new flat is generated on the surface of the diamond.

During this second phase of r the method, abrasion will take place in a plane or family of planes which is inclined relative to the initial plane but in the 110) direction offering maximum resistance to abrasion.

Again, when abrasion in this manner has generated a second critical flat, dressing operations are momentarily terminated and the previously generated edge of the critical flat in the dodecahedron plane, not selected for dressing purposes in the second phase of the method, is now selected and this edge is applied to the grinding wheel and a second new position is given the diamond by lateral angular displacement thereof wherein the tool is restored to the head-on position to permit the new edge existing by virtue of the intersection between the two previously generated critical flats to be presented squarely to the surface of the wheel. This last mentioned edge will exist in the crystal structure as a counterpart of the (110)-directed line originally selected for dressing purposes in the first phase of operations and, the diamond as a whole will assume the same relative position with respect to the plane of the grinding wheel that it assumed when grinding operations were initially commenced so that a complete three-phase cycle of operations will have been completed. This identical cycle may be repeated indefinitely until such time as the grinding wheel is considered to be sutiiciently dressed or until such time as the stone has become worn beyond any further usefulness, at which time a large percentage of the bulk of the diamond will have been consumed.

In practicing the method briefly outlined above, it should be noted that during each of the dressing phases described, abrasion takes place either in the (110) direction of the dodecahedron plane or parallel to the (110) direction as the lateral positions approach the (111) plane of the diamond. The diamond is highly resistant to abrasion throughout the angular displacement involved. It should be further noted that the direction of abrasion on the diamond is always parallel to the plane of rotation of the grinding Wheel and is normal to a radius of the wheel at the point of dressing contact.

The provision of a method such as has briefly been outlined above may be regarded as constituting one of the principal objects of the present invention.

As will become more readily apparent subsequently as the following description ensues, another important object of the invention is to provide a novel apparatus or mechanism whereby the position of the diamond dressing stone may be selectively altered relative to the rotating surface of the-grinding wheel at the beginning of each phaseof operations in conducting-the present method toward the'end thatthe (110) direction of'the dressing edge may be preserved as previously outlined. To accomplish this, the tool and tool holder assembly are so designed that the tool shank, and-consequently the diamond carried thereby and initially mounted in the shank with its crystallographic axes assuming a precise predetermined position relative to the shank axis, may be swunglaterally about a pivotal axis in either direction through an angle which is calculated according to engineering-exigencies to bringthe newly generated and selected dressing edge at the end of each dressing phase of the method, as outlined above, into. register with the surface of the grinding wheel in such a manner that the direction of feed of the tool assembly will cause wear to take place on the surface of the diamond in a direction which is at all times parallel to the 110) direction where, as previously stated, resistance to abrasion is of a superior nature. It has been ascertained that movement of the tool shank laterally throughout an angle of approximately 18 in one direction or the other about an axis'extending at a right angle to the axis of rotation of the wheel and normal to the radius of the Wheel at the point of contact between the wheel periphery and the diamond will effect the desired presentation of the diamond to the wheel for optimum truing .or dressing conditions at the commencement of any given dressing phase. It will be understood, however, that the tool and tool holder assembly may be designed for lateral displacements of greater or lesser than 18 ineither direction without destroying the essential features of the present method.

In connection with conventional methods and apparatus for dressing grinding wheels, utilizing a diamond dressing stone, it has been found that a diamond in any position of orientation will fracture along cleavage planes of least resistance if the area ofthe generated flat becomes sufliciently large. This phenomenon has been ascribed variously to the generation of heat under the influence of frictional forces, as well as to the disruptive elfectof such frictional forces. It is believed that due to the low thermal coefficient of expansion of the diamond that the above mentioned disruptive forces are due principally to the creation of drag on the surface of the flat undergoing generation at any given time and that when a relatively large flat is generated during dressing operations only the leading edge of the flat is performing a true dressing operation while all other trailing portions of the flat are creating a drag and a consequent burnishing action which places undesired mechanical stresses on the crystal structure of the diamond and causes the same to fail. The steps involved in practicing the present method of dressing a grinding wheel are calculated to reduce the deleterious effect of such phenomenon to a minimum and, accordingly, it is contemplated that in the preferred embodiment of the method the particular stone selected for dressing purposes will be of rounded configuration having receding lateral faces approaching the octahedron, dodecahedron or tetrahexahedron planes and that the stone will be so oriented and fixedly mounted in the tool shank that the portion of the stoneaddressing the Work, in any of the three positions of which the tool shank is capable of assuming, shall exist truly in the dodecahedron plane or parallel to the (110) direction, the former condition existing during first phase dressing operations and the latter condition existing during second and third phase dressing operations. It is further contemplated that the tool shall be fed in a direction such that abrasion will take place in the (110) direction which, as previously stated, offers a relatively high resistance to abrasion.

The natural dodecahedron face or the intersection of thenatural octahedron faces may be selected for presentation to the wheel for the first phase of dressing operations, or, alternatively, the dressing edge maybe created by artificial-means wherein the stone is mechanically shaped to reduce the angle between the lateral faces,- thus also reducing the area of contact between the diamond and the grinding wheel during dressing operations. In any event, however, it is preferable. that the narrowest or most acute edge which will present the smallest area of contact to the grinding wheel during the initial truing phase is first presented to the work and dressing operations are commenced as set forth above and continued until a critical flat is developed on the surface of the diamond. The tool shank is'then adjusted to either of the positions of which it is capable by swinging the same laterally in one direction or the other throughout the predetermined angle inthe direction which will bring one or the other edge of the previously generated flat into potential register with the periphery of the grinding wheel for the second phase truing operation. The third phase truing operation is carried out in the same manner, again selecting for presentation to the wheel either of the two available dressing edges remaining on the stone. The procedure is continued until such time as there no longer remains on the stone a suitable dressing edge. By such a procedure it will be apparent that large flats are avoided and such flats as must necessarily be presented to the grinding wheel are reduced to a minimum area to avoid the attendant generation of frictional forces which, otherwise, might have a disruptive effect upon the physical structure of the diamond.

The avoidance of unduly large flats during grinding wheel dressing operations may, according to the present invention further be avoided by the judicious selection of stones having natural dodecahedron, tetrahexahedron and octahedron characteristics wherein the exposed surfaces of the stone on opposite sides of the flat undergoing generation during a given dressing operation or phase will increase at a lower rate than in the case of a stone of comparable width of rectangular or slab-like section due to the receding extent of the line of intersection of the generated flat with each successive plane encountered in the family of planes progressively intersected as dressing operations proceed. For example, where natural dodecahedron faces are exhibited, the rhombic shape or outline thereof presents converging planes which, when intersected by the constantly changing generated plane of the flat, largely offset the constantly increasing area of contact afforded as the surface of the grinding wheel makes contact with otherwise adjacent divergent surfaces.

Stillfurther advantages of the present method will accrue from the selection of diamond dressing stones having dodecahedron, tetrahexahedron and octahedron characteristics, particularly if the exposed faces are of a curved convex nature as frequently they are. in their natural state. In such instances, as will be pointed out in more detail subsequently, the receding curved surfaces afforded by these stones remain out of contact with the surface of the grinding wheel undergoing dressing and contribute nothing toward an increase in area of the generated flat While at the same time they reenforce the regions of the stone which slope away from the generated flat and provide what is termed herein a buttress effect which isconducive toward preservation of the lateral faces of the stone and of those faces which underlie the trailing edges of the stone.

Under certain circumstances a narrow diamond. slab will be found ideal for use according to the present method'if it is oriented according to the principles of the invention as outlined above. In general however, the present invention obviates the necessity of selecting stones for their initial shape characteristics since all diamonds have the same inherent crystallographic.structure and, once the diamond has been properly set up with its direction parallel to the direction of abrasion and normal to.,the surface of the grinding wheel as outlined above, the phases of operation contemplated by the invention can be followed and the various truing edges generated, regardless of the original geometric configuration of the stone.

The provision of a method and apparatus for truing the peripheral surfaces of grinding wheels of the character and possessing the advantages set forth above being among the principal objects of the invention, numerous other objects and advantages thereof, not at this time enumerated, will become more readily apparent as the following description ensues.

In the accompanying four sheets of drawings forming a part of this specification, the various aspects of the present method outlined above have been diagrammatically illustrated, and the apparatus by means of which the method may be carried out is also illustrated.

In these drawings:

Fig. l is a fragmentary top plan view of a dressing tool assembly constructed in accordance with the principles of the present invention and showing the same operatively associated with a grinding wheel, the surface of which is to be dressed;

Fig. 2 is a side elevational view of the structure shown in Fig. 1;

Fig. 3 is a front end elevational view of the structure shown in Fig. 1;

Fig. 4 is a schematic top plan view, utilizing the structure of Fig. 1 and illustrating certain critical angles of orientation of the diamond dressing stone relative to the grinding wheel which are employed in practicing the present method;

Fig. 5 is a front elevational view of the schematic representation of Fig. 4;

Fig. ,6 is a side elevational view of the schematic representation of Fig. 4;

Figs. 7a, 7b and 7c are schematic representations illustrating the wear eifect which takes place on the diamond dressing stone during the three phases of the present method, respectively;

Fig. 8 is a side elevational view, somewhat schematic in its representation, illustrating the wear effect on a diamond stone of generally octahedron configuration when practicing the present method;

Fig. 9 is a side elevational view similar to Fig. 8 showing the wear effect when a rectangular diamond slab is employed;

Fig. 10 is a side elevational view similar to Figs. 8 and 9 showing the wear effect on a diamond having a generally rounded or tetrahexahedron configuration; and

Fig. 11 is a schematic plan view in the form of a chart representing the wear characteristics of a diamond actually employed for grinding wheel dressing purposes according to the present method.

Referring now to the drawings in detail and in par ticular to Figs. 1 to 3, inclusive, a tool and a tool holder assembly of novel design and designed for use in practicing the method of the present invention has been designated in its entirety at 10. The assembly 10 involves in its general organization a tool in the form of a shank, slug, or mount 12, as it is variously termed, carrying a diamond 14 at its forward end. The shank 12 is preferably in the form of a rectilinear block which is substantially square in transverse cross section and 'which is elongated longitudinally. The forward end region of the shank 12 is tapered to provide a frustopyramidal front end portion 16, the forward face or small base of which carries centrally thereof the cutting tool proper or diamond 14. The external configuration or shape of the diamond 14, especially the configuration of the forwardly exposed surface thereof, may vary within certain limits to better accommodate different installations, grinding Wheels having different textures, hardness, diameters, etc., and it may also vary somewhat for each particular installation as will he described subsequently. However, the arrangement of the inherent crystallographic axes in the isometric system of crystallization of the diamond relative to the longitudinal and transverse directions of the shank 12 are predetermined within very fine limits regardless of the nature of the work or of the particular diamond selected for truing operations in order to effect presentation of the diamond to the work in varying angular positions according to the method of the invention when the shank is adjusted to any of the positions of which it is capable of assuming.

The shank 12 is adapted to be adjustably mounted on a holder 18 which is preferably of one-piece construction and includes a stem portion 20 designed for attachment to a slide or carriage (not shown) by means of which the tool assembly 10 is traversed across the face of the grinding wheel. It will be understood, of course, that in certain installations, the tool assembly 10 will be maintained stationary and the rotating grinding wheel will traverse the tool. Irrespective, however, of the particular means whereby the tool and grinding wheel are caused to move laterally relative to one another, the essential features of the invention are at all times preserved. The forward end of the stem 20 is provided with a clamping head 22 from which there extends forwardly a shelf-like portion 24 of generally triangular configuration and providing a flat, upwardly facing clamping surface 26 against which the shank 12 is adapted to be securely clamped in any one of three possible positions of adjustment with the shank in either its upright position or in an inverted position. Accordingly, the shank 12 is formed with a vertical bore 28 therein in the forward regions thereof designed for registry with a similar bore 30 provided in the shelf portion 24. A combined clamping screw and pivot member 32 passes through the bore 30 and is threadedly received in the bore 28 and is formed with an enlarged head 34 which seats against an undercut portion 36 provided in the shelf portion 24 when the clamping screw 32 is tightened in the bore 28. The shelf portion 24 is formed in the rear regions thereof with an arcuate series of three equidistantly spaced holes 38, 40 and 42, respectively, designed for selective register with a threaded hole 44 formed in the rear portion of the shank 12. A clamping screw 46 extends and is selectively receivable through the holes 38, 40 and 42 and is adapted to be threadedly received in the hole 44 to thus determine the various adjusted positions of the shank 12 relative to the holder 18. An enlarged head 48 on the clamping screw 46 is adapted to bear against an undercut portion 50 of the shelf portion 24 for clamping purposes when the clamping screw 46 is tightened.

Still referring to Figs. 1 to 3, inclusive, a fragmentary portion of the grinding wheel undergoing truing is designated at 52, the direction of rotation of the wheel being shown by the arrow in Fig. 2. As best seen in Figs. 1 and 2, the direction of feed of the tool and holder assembly is radially inwardly of the wheel 52 and, when the shank 12 is in its center position with the holes 40 and 44 in register with each other, the central longitudinal axis of the shank 12 passes substantially centrally through the diamond 14 and intersects the axis of rotation of the wheel 52. The axis of the shank extends horizontally in the illustrated form of the assembly although it is within the purview of the invention that this axis shall extend along other radial planes of the wheel 52.

It is to be noted that the circumferential spacing of the holes 38, 40 and 42 about the vertical axis of lateral angular turning movement of the tool shank 12, i. e., the axis of the clamping screw 32, is such that the shank may be displaced from its center position throughout equal angles either to the right or to the left as shown in dotted and broken lines respectively in Fig. 1. These equal angles of displacement are designated 6 and 0 respectively and they may assume diiferent magnitudes within. operable limits,tovary;the-:angles of displacement of-the tool shank fromits centered position .on the :holder and thus change the position; of the diamond =14 for purposeswhichwill bemade: clear subsequently. In the illustrated embodiment of the, invention, the angles and 0' are each of 18 magnitude since this magnitude has been found to be appropriate. for most dressing operations, utilizing diamonds having. average, shape characteristics. It has :been found, however, that the tool and holder assembly. may be designed for displacements of from 6 to 30 in either direction in the performance of special-grinding operations .or to accommodate stones having specific shapes.

Referring now to Figs. 7a, 7b and 70 whereinthe method of thepresent invention is more or lessschematically. illustrated, and disregarding for the moment the; specific external :shape. of the diamond 14-associated with the shank 12, the three phases of truing operations extending through one complete truing-cycle have been portrayed, utilizing, shaded areas to designate the effects of wear on the stone by the rotating grinding wheel 52 and utilizing suitable legending to enhance the disclosure. The diamond v14, regardless of its shape characteristics, is mountedjin the. shank. 121 in aprecise and predetermined manner wherein the (110) crystallographic axis extends. atan angle of 90 to the underneath or base surface 54 (Fig. 2) of'the rectilinear shank 12. This relationship is geometrically illustrated in Figs. 4 to 6, inclusive, whereinthe critical angles of orientation of the diamond 14 relative to the shank 12 and to the grinding Wheel 52. portrayed are applicable to any selected; diamond regardless-of its external shape characteristics, The longitudinal axis-of the shank is designated at ,aa in Fig. 4 andthesides 56 and 58 of the shank extend parallel tovthis axis and at right angles to the base 54. The generally vertical linear ridge or edge 60 which appears as a line in Figs. 5 and 6 andas an endon point=in Figs. 4 and 7a, extends parallel to the (110) direction and -it .may be an artificially created edge or it may be a natural ridge on the surface of the diamond.

During the first phase of truing operations, the shank 12 .isgpositioned on. the holder 18 -in such amanner that the edge 60 is presented to'the surface of therotating grinding wheel head-on. First phase truing operations are. commenced as shown in Fig. 7a and the tool and holder assembly is fed radially inwardly toward the grinding wheel axis horizontally and the shaded area designated at 64 in Fig. 7a is gradually worn away until such time as a critical flat 66 on the surface of the diamond 14 is created. At thistime, two edges 68 and 70 will have been generated in the truing operation, each of which exists at the intersection of the flat 66 and one of the lateral surfaces 72-and 74 of the diamond 14 on opposite sides thereof and each of which extends parallel to the (110) direction. Truing operations are then terminated preparatory to readjustment of the position -of the shank 12 for second phase truing operations.

Either edge 68 or 70 may be selected for second phase truing operations and the selected edge is adjusted so that this edge is presented to the wheel 52. The adjustment is made by loosening the two clamping screws 32 and 46, and then removing the screw 46 from the holes 40 and 44 and passing it through either the hole 38 or 42, as the case may be, depending upon which of the two edges 68 or 70 isselected for truing operations and causing it to again be threadedly received in the hole 44. Assuming for illustrative purposes that the edge 70 is selected, the screw 46 will be threaded into the bore 42 and the two screws 46 and 32 tightened so that the shank 12 will be firmly clamped .in the position shown in broken lines in Fig. 1 and in Fig. 7b wherein it is laterally angularly displaced 18 from its original position. During secondphase truing operations, the

1G tool-{andholder assembly 10 'is' fed radially inwardly of the grinding wheel asin the first phase grinding operation and'a second critical flat 76 -is generated while'the shaded area 78 is worn away. Generation of the flat-76 serves torestablish two newly, generated edges 80-a-nd82 on the surface of the diamond 14, each of which extends parallel to the (110) direction. The edge 80 lies atthe intersection of the original flat 66 andthe secondly formed flat 76, while the edge 82 lies at the intersection of the flat 76 and the lateral face-74 of the diamond.

As an alternative procedure for second phase truing operations, it is contemplated that the shank 12-may be inverted on the holder 18' in such a manner as to bring either the hole 38 or 42 into register with the hole 44 and the clamping screw 46inserted into the registering holes so that when the edge 68 -or 70 which has been selected for truing operations 'isbrought into register with the surface of the wheel 52, it will have been turned endto-end while its direction will still extend parallel to the 110) direction. By such an-expedient, it is often possible to select a more judicious orientation of the diamond relative to the grinding wheel surface for truing purposes inasmuch as sparse regions of the diamond surface initially existing below the level of truing operations, and which ordinarily would be subject to chipping, may be avoided and a more substantial region existing initially on the surface of the diamond above the level of truing operations may be positioned so as to have a buttressing 'eifect on those regions of the diamond which are placed under stress during truing operations as previously described. In certain instances second phase operations may be conducted merely by inverting the shank 12 .on' the holder 18 so that the holes 40 and 44 remain in register while the axis-of the shank 12 maintains its head-on relation. Such a rearrangement. of the stone may be resorted to in instances, for example, where the upright position of the diamond has resulted in chippingor has otherwise not proven satisfactory.

For a third phase truing operations, the edge 68 which was not selected for second phase truing operations is now selectedand the position of the shank 12 is adjusted accordingly in eitherthe upright or inverted position so that this latter edge is presented to the surface of the grinding wheel 52 with the shank 12 being angularly displaced 36 from the position it assumed during second phase operations or 18 from its original position as shown in dottedlines in Fig. l and in Fig. 70. Again, the tool and holder assembly 10 is fed radially inwardly of the grinding wheel 52' in .a horizontal'direction and a third critical flat 84 is generated and two new edges 86 and 88am created, both ofwhich. extend in adirection parallel to the (11.0) direction of the diamond. During suchthird phase truing operations, a shaded area 90 is worn away as shown in Fig. 7c. The. edge 86 will lie. at the intersection between the flat 84 and the lateral edge ,72, while the edge 88 will lie at the intersection of the fiat 84.with the flat 76 generated during the second phase of operations. It will be observed that when truing operations are terminated, the condition of the diamond 14 will be such that the edge 88 and the two flats .84 and 76 on opposite sides thereof bear the same geometrical relationship to the diamond as a whole as the initial truing edge 60 and its sidesurfaces. Thus, the edge 88 is available for truing purposesat the commencement of the second cycle of truing operations which may be carried out in the same manner and by the same procedure as that outlined abovein connection with the ,first three phase cycle of operations. The operations are repetitive untilsuch time as the diamond 14 has been completely worn and can perform no further-useful purpose. Resetting operations are ordinarily notcontemplated and the shank, together with-the worn outdiamond therein may be discarded and a new shank withdafresh diamond, suitably mounted-as heretofore 11 described may be substituted in its stead if further grinding operations on the wheel are necessary.

The procedure set forth above in connection with the disclosure of Figs. 7a, 7b and 7c is applicable, with or without modification as required, for any appropriate diamond regardless of its dimensional characteristics. In Figs. 4, and 6, the geometrical relationships set forth above in connection with the shank 12 and diamond 14 of Figs. 7a, 7b and 70, as well as in connection with any suitable diamond mount have been illustrated. The dotted lines at 100 complete the outline of a true octahedron and the dotted lines at 102 and 104 illustrate how such a stone may be modified to produce the generally rounded type of stone described in connection with Figs. 7a, 7b and 70, or a slab-type of stone respectively.

In Fig. 8, the shank 112 has mounted therein a diamond 114 exhibiting octahedron characteristics and the shank is shown as being disposed in its head-on position relative to the wheel. Utilizing similar reference numerals to those employed in connection with Figs. 7a, 7b and 7c but of a higher order to avoid needless repetition of description, the initial truing edge 160 extends parallel to the (110) direction of the diamond and the shaded areas 161 and 163 represent the wear facets involved in the truing operation on one side of the diamond. These facets are generated during the first and second operating cycles respectively and the form of shading employed illustrates the fact that successively formed facets or flats formed on the surface of the stone are of increasing width.

In Fig. 9 a similar representation of a diamond mount involving a diamond slab 214 having rectangular characteristics has been made. Again, utilizing reference characters of a still higher order, the initial truing edge 260 extends parallel to the (110) direction of the diamond 214 and the first two wear facets on one side of the stone involved in the truing operation during the first two cycles are shown at 261 and 263, respectively. In this instance, instead of commencing the cycle with the longitudinal axis of the shank 212 intersecting the axis of rotation of the grinding wheel and feeding the diamond in the headon manner set forth previously, truing operations are commenced on an 18 angle, utilizing one or the other lateral forward edges of the rectangular slab as the initial truing edge. During second phase truing operations, the tool shank is moved throughout an angle of 36 to bring the other lateral forward edge into register with the wheel. After second phase truing operations are completed, the third phase will commence with the tool shank in its centered position so that the edge which has been generated at the intersection between the critical flats worn during first and second phase truing operations will then be available for final phase truing operations.

In Fig. a representation similar to Figs. 8 and 9 but involving a diamond 314 having tetrahexahedron characteristics has been made. The first truing phase of the truing process in the illustrated form of diamond is made with the shank 312 at one of its 18 angularly oifset positions and thus the shaded areas 361 and 363 represent the wear facets created during first phase truing operations in successive cycles on one side of the stone.

The representations of Figs. 8, 9 and 10 are illustrative of typical stones which may be employed in connection with the present method and it will be understood that stones having other shape characteristics in the isometric system may be employed if desired without departing from the principles of the present invention.

In Fig. 11 the wear characteristics of typical diamond 414 employed for grinding wheel dressing purposes ac cording to the present method has been shown in chart form. The wear life of the diamond extends through five cycles of operation involving fifteen truing phases. The various wear patterns have been designated sequentially from a through m in the alphabet of designations. The various truing edges, all of which extend parallel to the (110) direction of the diamond have not been specifically designated to avoid confusion. However, it will be understood that in certain of the three-phase cycles of operation, the left lateral displacement and the right lateral displacement of the tool were interchanged to first bring one edge or the other into register with the grinding wheel as previously described. Fig. 11 is also illustrative of the fact that the so-called edges or ridges such as the edges or ridges 60, 68, 70, 86, 88, etc. shown in Figs. 7a, 7b and 7c, will not necessarily in every instance assume a sharp form. They may assume the form of blunt edges or of narrow flats in certain instances, as, for example, where a flat becomes critical at an early stage in any particular phase or for other reasons.

It will be understood that throughout this specification, many of the terms employed herein are employed in a broad sense which may be slightly at variance with dictionary definitions but which, considered in their broad sense are not inconsistent therewith. For example, it has been stated herein that certain critical flats are generated on the surface of the diamonds 14, 114, 214, etc. by contact of the diamond with the peripheral surface of the grinding wheel 52. Since the surface of the wheel is of a curved nature, it is obvious that the socalled flats may not be actually planar. However, any curvature existing in connection with such flats is possessed of such a long radius that for practical purposes itihese surfaces may be regarded as being substantially It will also be understood that the terms dressing and truing as employed herein are intended to mean con- .trolled removal of stock from the surface of a rotating grinding wheel by effecting relative traversing movement of the wheel and diamond after the same have been adjusted relative to each other so as to bring the diamond into traversing register to a depth corresponding to that at which stock is to be removed from the wheel. Such dressing or truing is applicable to the removal of stock from the corners or end faces of a grinding wheel, as well as from a peripheral surface or any combinations thereof.

It has been found that satisfactory truing operations on the surfaces of a grinding wheel may be attained when any of the truing procedures described herein are conducted if the direction of the diamond does not deviate more than five degrees in either direction from true parallelity with the direction of abrasion. It is contemplated that the term parallel, as employed herein, shall be construed to include substantial parallelity within the extent of deviation mentioned above.

From the above description it is thought that many inherent advantages of the present method will be apparent and it should be understood that in order to attain these advantages to the fullest extent, minor variations in procedure in practicing the method may be resorted to without departing from the spirit of the invention. The invention, therefore, is not to be limited to the exact sequential steps set forth above in describing the truing {procedure associated with specific diamond shapes selected for illustration, nor is it to be limited to the exact arrangement of tool and tool holder parts shown in the drawings and described in this specification since departures from the specific steps described and from the details of construction may be resorted to without departing from the concept of the invention. Only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

Having thus described the invention What we claim as new and desire to secure by Letters Patent is:

1. The method of truing a surface on a rotating abrasive grinding wheel which utilizes a diamond dressing stone and which comprises selecting a prominent edge on the face of the stone and applying the stone to the rotating surface of the wheel so that said edge engages the wheel surface at the desired depth while simultaneously maintaining the (110) direction of the stone, according to Millers crystallographicsystem of notation, parallel to the direction of abrasion, effecting relative traversing movement between said stone and wheel surface without altering the directional orientation-of the stone relative to the wheel whereby abrasion of the stone will take place andaflat will be progressively generated on the wheelcontacting surface thereof While at the same time a pair of potential truing edges will be generated along the lateral sides of said flat respectively, selecting one of said potential truing edges and applying the same to, the rotating surface so that the edge engages the rotating surface at thedesired depth while maintaining the (110) direction of the stone parallel to the direction of abrasion, effecting relative traversing movement between said stone and surface without appreciably altering the directional orientation of the stone relative to the wheel pefip'hery whereby abrasion of the stone will take place and a second flat will be progressively generated on the wheel-contacting surface thereof while at the same time a linear edge will be generated at the intersection between said first and second flats, applyingthe other potential truing edge to the rotating surface so that the same engages the rotating surface at the desired depth while maintaining the (110) direction of the stone parallel to the direction of abrasion, effecting relative traversing movement between the stone and surface without appreciably altering the directional orientation of the stone relative to the wheel surface so that abrasion of the stone willtake place and a third flat will be progressively gen- 'erated on the wheel-contacting surface while at the same time a linear edge will be generated at the intersection of'said first and third flats in the vicinity of the intersection between said first and second flats, thus creating a ridge in the plane of the first flat which extends parallel to: the (110) direction of the stone and which bears the same positional relation to diamond structure as the initially selected prominent edge.

2. The method oftruing a surface on a rotating abrasive grinding wheel which comprises, selecting a prominent point on the surface of a diamond dressing stone and applying the stone to the rotating surface of the wheel so that the point engages said surface while simultaneously maintaining the 110) direction of the stone, according to Millers crystallographic system of notation, parallel to thedirection of abrasion, effecting relative traversing movement between said stone and surface without appreciably altering the directional orientation of the'stone relative to the wheel whereby truing of the surface and abrasion'of the stone will take place and a flat will be progressively generated on the wheel-contacting surface thereof while at the same time a potential truing edge will be generated along at least one lateral side of the flat, thereafter applying said truing edge to the rotating surface of the wheel so that said truing edge engages the surface while simultaneouslymaintaining the (110) direction-of the stone parallel to the direction of abrasion, and effecting relative traversing movement between said stone and surface Without appreciably altering the directional orientation ofithestone relative to the Wheel periphery.

3.2The method of truing a surface on a. rotating abrasive grinding wheel which comprises. applying the surface of a diamond dressing stone to the rotating peripheral surfaceof the wheel while simultaneously maintaining the (110) direction of the stone, according to Millers crystallographic system of notation, parallel to the direc: tion of abrasion, effecting relative traversing movement between the stone and wheel without appreciably altering the directional orientation of the stone relative to the Wheel periphery whereby truing of the Wheel surface and abrasion of the stone will take place and a flat will be progressively generated on the wheel-contacting surface of the. stone while at the same time a pair of potential truing edges will be created along the lateral sides of the flat respectively, and thereafter utilizing said' potential truing edges successively by applying them to the rotat- 1'14 ing surfaceof the wheel'while simultaneously maintain: ing. the direction-ofthe stoneparallel to the direction of :abrasion.

4.- The method of truing a surface on a rotating abrasive grinding wheel which comprises applying the surface of a diamond dressing stone to the rotating surfaceof the wheel-while simultaneously maintaining the (110) direction of the stone, according to Millers. crystallographic system of notation, parallel to the direction of abrasion, effecting relative traversing movement between the stone and wheel periphery without appreciably altering the directional orientation of the stone relative to the wheel whereby truing of the wheel surface and abrasion of the stone will take place and a flat will be progressively generated on the wheel-contacting surface of the stone while at the same time a potential truing edge will be created along one lateral side of the flat, and thereafter utilizing said potential truing edge for wheel truing purposes by applying the same to the rotating surface of the wheel while simultaneously maintaining the (110) direction of the stone parallel to the direction of abrasion, and effecting relative traversing movement between the stone and wheel periphery Without appreciably altering the directional orientation of the stone relative to the wheel periphery.

5. The method of truing a peripheral surface on a rotating abrasive grinding wheel which comprises effecting a first three-phase cycle of truing operations by applying the surface of a diamond truing stone to the rotating surface of the wheel while simultaneously maintaining the (110) direction of the stone, according to Millers crystallographic system of notation, parallel to the direction of abrasion, effecting relative traversing movement between the stone andwheel periphery without appreciably altering the directionalorientation of the stone relative to the wheel periphery whereby truing of the wheel surface and abrasion of the stone will take place and a flat will be progressively generated on the wheelcontacting surface ofthe stone while at the same time a pair of potential truing edges will be created along the lateral sides of the flat respectively, selecting one of said potential truing edges and displacing the diamond angularly and laterally so as to bring said selected edge into traversing register with the wheel periphery while maintaining the (110) direction of the stone, according to Millers crystallographic system of notation, parallelto the direction of abrasion, effecting a second phase of truing operations by traversing the stone and wheel relative to each other without appreciably altering the directional orientation of the stone relative to the Wheel whereby abrasion will take place and a second flat will be generated progressively on the wheel-contacting surface thereof while at the same time a linear edge will be created at the intersection between said first and second flats, displacing the diamond'angularly and laterally to bring the other potential truing edge into traversing register with the wheel while maintaining the (110) direction of the stone parallel to the direction of abrasion, effecting a third phase of truing operations by traversing the stone and wheel relative to each other without appreciably altering the directional orientation of the stone relative to the wheel whereby abrasion will take place and a third flat will be generated progressively on the wheelcontacting surface thereof while at the same time a linear edge will be generated at the intersection of said first and third flats in the vicinity of the intersection between said first and second flats, thus creating a ridge extending parallel to the (110) direction of the stone, and repeating said cycle of truing operations utilizing said ridge as a truing edge for the first phase truing operation in the second cycle.

6. The method of truing a surface on a rotating abrasive grinding wheel which comprises applying the surface ofa diamond dressing stone to the rotating surface. of the Wheel while simultaneously maintaining the (110) direction of the stone, according to Millers crystallographic system of notation, parallel to the directionof abrasion, effecting relative traversing movement between the stone and wheel periphery without appreciably altering the directional orientation of the stone relative to the wheel whereby truing of the wheel surface and abrasion of the stone will take place and a flat will be progressively generated on the wheel-contacting surface of the stone while at the same time a pair of potential truing edges will be created along the lateral sides of the flat respectively, and thereafter utilizing said potential truing edges successively by applying them in the order of sharp ness of the angle subtended by the intersecting sides thereof to the rotating surface of the wheel while simultaneously maintaining the (110) direction of the stone parallel to the direction of abrasion.

7. The method of truing a peripheral surface on a rotating abrasive grinding wheel which utilizes a diamond dressing stone in the form of a slab having substantially parallel lateral sides and a forward face extending between said lateral sides and wherein the lateral edges of said forward face at the intersection of the latter with said lateral sides extend parallel to the (110) direction of the stone, according to Millers crystallographic systern of notation, said method comprising applying said stone to the rotating surface of the wheel so that one of said edges engages said surface while simultaneously maintaining the (110) direction of the stone parallel to the direction of abrasion so that said one edge extends in the (110) direction, effecting relative traversing movement between said stone and surface without appreciably altering the directional orientation of the stone relative to the wheel whereby truing of the surface and abrasion of the stone will take place and a fiat will be progressively generated on the wheel-contacting surface thereof while at the same time an edge will be created at the intersection between said flat and said forward face, and thereafter applying said latter edge to the rotating surface of the wheel so that said latter edge engages the surface While simultaneously maintaining the (110) direction of the stone parallel to the direction of abrasion, and effecting relative traversing movement between said stone and surface without appreciably altering the directional orien tation of the stone relative to the wheel periphery.

8. The method of truing a surface on a rotating abrasive grinding wheel which comprises applying a diamond truing stone to the rotating surface of the Wheel while simultaneously maintaining the (110) direction of the stone, according to Millers crystallographic system of notation, parallel to the direction of abrasion, thus generating spaced truing edges on the surface of the stone which are available for subsequent truing purposes, and thereafter repeatedly shifting the stone angularly to bring first one and then another of said truing edges into truing contact with the rotating surface of the wheel While still maintaining the (110) direction of the stone parallel to the direction of abrasion, thus causing new truing edges to be regenerated on the surface of the stone, and theresaid bottom face and parallel to said sides, and means associated with said shank whereby the same may be adjustably positioned on a mount holder in selected positions of angular adjustment.

10. A diamond mount designed for use in truing the peripheral surface of a rotating grinding wheel, said mount comprising a metal tool shank which is rectangular in transverse cross section and having parallel sides and a bottom face, and a diamond truing element fixedly mounted at the forward end of said shank with its (110) direction, according to Millers system of crystallographic notation, extending at approximately a right angle to said bottom face and parallel to said sides, the extreme forward end of said diamond being formed with a truing edge extending generally in the (110) direction of the diamond, said truing edge being designed for initial presentation to the peripheral surface of the grinding wheel so that it extends parallel to the direction of abrasion with the axis of the shank intersecting the axis of rotation of the grinding Wheel, and means associated with said shank whereby the same may be adjustably positioned on a mount holder in selected positions of angular adjustment.

11. In a tool assembly for truing the peripheral surface of a rotating grinding wheel, a holder having an upwardly presented fiat shelf-like supporting surface, a diamond mount supported on said surface and adapted to be clamped thereto in selected positions of angular adjustment, said diamond mount comprising an elongated shank having a flat bottom surface positioned in face-to-face contact with said shelf surface, a truing diamond fixedly carried at the forward end of the shank, the forward end of said shank projecting forwardly beyond the confines of said holder, said shank being formed with a vertical bore in the forward regions thereof, said holder being formed with a vertical bore in register with said here in the shank, one of said bores being interiorly threaded, a clamping bolt threadedly received in said threaded bore and extending through said other bore, and clamping means for selectively clamping the rear region of said shank to said supporting surface in a plurality of angular positions thereon about the axis of said clamping bolt. 12. The method of truing a surface on a rotating abrasive grinding wheel which comprises applying the surface of a diamond dressing stone to the rotating peripheral surface of the wheel while simultaneously maintaining the (110) direction of the stone, according to Millers crystallographic system of notation, parallel to the direction of abrasion, effecting relative traversing movement after further repeatedly shifting the stone angularly to bring certain of the regenerated truing edges into truing contact with the rotating surface of the wheel in a similar manner and continuing the process indefinitely until such time as the stone has been worn beyond further usefu-lness, each truing operation being carried out with the (110) direction of the stone being maintained parallel to the direction of abrasion.

9. A diamond mount designed for use in truing the peripheral surface of a rotating grinding wheel, said mount comprising a tool shank which is rectangular in transverse cross section and having parallel sides and a bottom face, and a diamond truing element fixedly mounted at the forward end of said shank with-its (110) direction, according to Millers crystallographic system of notation, extending approximately at a right angle to between the stone and wheel without appreciably altering the directional orientation of the stone relative to the wheel whereby truing of the wheel surface and abrasion of the stone will take place and a flat will be progressively generated on the wheel-contacting surface of the stone while at the same time a potential truing edge will be created along one lateral side of the flat, and thereafter inverting said diamond by turning the same throughout an angle of 180 and utilizing said potential truing edge for wheel truing purposes by applying the same to the rotating peripheral surface of the wheel with the diamond thus inverted while simultaneously maintaining the direction of the stone parallel to the direction of abrasion, and effecting relative traversing movement between the stone and wheel without appreciably altering the directional orientation of the stone relative to the wheel.

References Cited in the file of this patent UNITED STATES PATENTS 2,292,957 Meeson et al. Aug. 11, 1942 2,302,921 Spencer Nov. 24, 1942 2,325,334 Meeson July 27, 1943 2,587,132 Finke Feb. 26, 1952 2,791,211 Nagy May 7, 1957 

